Electrophysiology/Cell Culture Core is designed to provide PPG investigators with an array of commonly utilized cultured human intestinal epithelial cell lines (Caco-2, T84, HT-29, and NCM460) and access to a multitude of electrophysiological measurements on both cultured epithelial sheets and native tissues. Both Core components house state-of-the-art equipment, which is run by personnel with full technical expertise so that training, assistance with experimental design, data collection, data analysis and interpretation are provided. This Core is under dual direction by Drs. Gail Hecht and Mrinalini Rao. They both have extensive experience in all aspects of electrophysiological measurements in cultured intestinal epithelia, native intestinal tissue, and primary intestinal cells. The Specific Aims are to provide the investigators and projects within this Program Project with human cultured intestinal epithelial cells including Caco-2, T84, HT-29, and NCM460 grown on plastic or permeable (Transwell) filters; electrophysiological measurements in Ussing chambers including short circuit current (Isc), transepithelial electrical resistance (TER), ion flux analysis, on both cultured intestinal sheets and native intestinal tissues; and spectrofluorometric measurements as a complementary approach to assessing ion transport. The provision of these cells for electrophysiologic measurements will facilitate and expedite the proposed experiments of all of the Program investigators and will standardize the conditions under which these cells are grown thus allowing for direct correlation of data obtained for each of the Projects.